1. Field of the Invention
This invention relates to network communication and, more particularly, to traffic shaping at network nodes for increasing the nodal connection-carrying capacity.
2. Description of Related Art
Networks are a principle way of exchanging or transferring information, such as signals representing voice, audio, text or video among communication devices. Such communication devices include devices for sending and/or receiving information, such as computer terminals, multimedia workstations, facsimile machines, printers, servers and telephones. The exchange or transfer of information is referred to as a call or connection. Information transmitted on the network can be of many different forms but is often formatted into fixed-length packets or cells.
A network typically includes switching nodes having ports coupled by links to ports of other switching nodes and to the communications devices. Each link is uni- or bi-directional and is characterized by a bandwidth or link capacity. Information to be exchanged is often conveyed over a path comprising a set of nodes and links connecting the communication devices. The path can be regarded as a virtual circuit (VC) whereby one communication device specifies the intended destination for the information, and the network delivers the information as though a dedicated circuit connected the two communication devices. Cells in transit between communication devices may temporarily be stored in buffers at nodes along the path of the virtual circuit pending sufficient available bandwidth on subsequent links along the path.
Networks, such as broadband ISDN (BISDN) employing asynchronous transfer mode (ATM) packet switching, are increasingly being used for the reliable, high-speed transmission of information. This increased use has brought major changes in network architecture and infrastructure design as well as in network operations and/or in the classes of services offered over the network. Classes of services offered over a network can include, for example, video-on-demand and video teleconferencing. Moreover, particular classes of services, such as video teleconferencing, are relatively sensitive to routing delays and receive higher priorities than other service classes, such as video-on-demand, which are relatively delay insensitive.
To obtain high revenues from a network, it is advantageous for network managers to operate the network at a relatively high call capacity, i.e. establishing and maintaining a large number of simultaneous VC's. The issue of congestion control is intertwined with the notion of the capacity of the network measured in users for given quality of service, and the administration of admission control in real-time, where the goal is to admit users up to capacity. The statistical nature of a significant part of the traffic, its burstiness and variability, and the stringency of the quality of service requirements combined pose challenges. An essential prerequisite in dealing with these challenges is the regulation of traffic at network edges.
Buffer memories are typically employed in the nodes to increase the number of VC's carried by the node by buffering transmission of data cells that are relatively delay insensitive while buffering to a lesser extent transmission of those data cells that are relatively delay sensitive. Such buffer memories, which can be relatively expensive, effectively operate as respective queues in the node for the data cells that are to be conveyed through the respective ports.
Therefore, a system is required to enhance the connection-carrying capacity for the network nodes in an efficient and cost-effective manner.